Seemingly out of nowhere, your little one is covered in small, angry-looking bumps. The first time your baby gets a heat rash, your big questions will likely be: "What is it?" "How did she get it?" and "How do we get rid of it?"

Simply put, heat rash is the skin's response to too much heat. Also referred to as prickly heat or miliaria, heat rash can affect anyone, but it's incredibly common in newborns and infants. Normally, when we start to sweat, perspiration travels up through the sweat ducts to the skin's surface and eventually evaporates. But babies are born with immature sweat ducts that can easily rupture.

Heat Rash Symptoms

Your pediatrician can confirm diagnosis but you're specifically looking for a rash with tiny red bumps surrounded by redness on the skin. It generally occurs on clothed parts of the body: Heat rash on the armpits, abdomen, and groin is common, says Parents advisor Jody A. Levine, M.D., director of dermatology at Plastic Surgery & Dermatology of NYC. In infants, you're looking for heat rash on the neck (a major heat trapper), shoulders, and chest, too. The rash can be accompanied by a pins-and-needles sensation, so watch for some possible scratching.

What Causes Heat Rash?

"The combination of your baby being in a warm environment and being over-clothed eventually causes prickly heat," says Parents advisor Lawrence F. Eichenfield, M.D., professor of pediatrics and dermatology at University of California, San Diego, and chief of pediatric and adolescent dermatology at Rady Children's Hospital-San Diego.

And a warm environment can take on many forms. "A hot summer day and a non-air-conditioned home can bring on a heat rash," says Dr. Eichenfield. "And if you overheat your home in the winter and keep the baby bundled up, that creates a high risk, too." Once your baby is officially overheated, she'll try to sweat, unsuccessfully, and develop a heat rash instead. To avoid this, you need to find the right balance between what she's wearing and where she's wearing it.

This video shows a 3 year old boy with scarlet fever. Common symptoms of scarlet fever are a high fever, a sore throat, difficulty swallowing, a headache and swollen lymph nodes in the neck. The child will also have a distinctive rash.

Heat Rash Cream and Other Treatments

Start by cooling both room and Baby. If it's summer, crank up the A/C a notch or put a fan in his room to lower the temperature. In winter, be sure to monitor your thermostat.

Dress him in lightweight, loose-fitting clothes that allow the affected areas to breathe. If he's scratching, heat rash ointment such as calamine lotion, anhydrous lanolin, or anOTC topical steroid like hydrocortisone cream may be used, according to the Mayo Clinic. "But only with your pediatrician or dermatologist's approval," says Dr. Levine. Some lotions and creams can block sweat and further irritate the skin.

Prickly heat usually clears up within in a few days, but can occasionally become a bigger problem. "Parents should watch out for deep-red areas and blisters," says Dr. Eichenfield. "It won't look like regular prickly heat." If the rash extends outside the usual areas—the clothed parts of the body—then it's time for another trip to your pediatrician or dermatologist.

How to Prevent Heat Rash

Think about the story Goldilocks and the Three Bears. Her porridge was too hot, then too cold, and finally, just right. The same concept can be applied to regulating your baby's body temperature—you're looking for "just right." This could involve a little trial and error but use yourself as a barometer: If you're too hot, there's a good chance she is, too. "A cool, dry environment will keep prickly heat at bay," says Dr. Levine.

Resist the urge to overdress. This means lightweight, cotton clothes in the summer and the appropriate amount of clothes in the winter. If you strike the right balance between his environment and attire, your baby should be able to avoid heat rash.

Before you take Baby to the park or pool this summer, be sure you know how to keep her comfortable and prevent her from getting overheated.